6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ard Biesheuvel <ardb@xxxxxxxxxx> commit d2d7a54f69b67cd0a30e0ebb5307cb2de625baac upstream. Instead of returning to the calling code in assembler that does nothing more than perform an indirect call with the boot_params pointer in register ESI/RSI, perform the jump directly from the EFI stub C code. This will allow the asm entrypoint code to be dropped entirely in subsequent patches. Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx> Link: https://lore.kernel.org/r/20230807162720.545787-4-ardb@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/firmware/efi/libstub/x86-stub.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -279,7 +279,7 @@ adjust_memory_range_protection(unsigned #define TRAMPOLINE_PLACEMENT_BASE ((128 - 8)*1024) #define TRAMPOLINE_PLACEMENT_SIZE (640*1024 - (128 - 8)*1024) -void startup_32(struct boot_params *boot_params); +extern const u8 startup_32[], startup_64[]; static void setup_memory_protection(unsigned long image_base, unsigned long image_size) @@ -760,10 +760,19 @@ static efi_status_t exit_boot(struct boo return EFI_SUCCESS; } +static void __noreturn enter_kernel(unsigned long kernel_addr, + struct boot_params *boot_params) +{ + /* enter decompressed kernel with boot_params pointer in RSI/ESI */ + asm("jmp *%0"::"r"(kernel_addr), "S"(boot_params)); + + unreachable(); +} + /* - * On success, we return the address of startup_32, which has potentially been - * relocated by efi_relocate_kernel. - * On failure, we exit to the firmware via efi_exit instead of returning. + * On success, this routine will jump to the relocated image directly and never + * return. On failure, it will exit to the firmware via efi_exit() instead of + * returning. */ asmlinkage unsigned long efi_main(efi_handle_t handle, efi_system_table_t *sys_table_arg, @@ -905,7 +914,10 @@ asmlinkage unsigned long efi_main(efi_ha goto fail; } - return bzimage_addr; + if (IS_ENABLED(CONFIG_X86_64)) + bzimage_addr += startup_64 - startup_32; + + enter_kernel(bzimage_addr, boot_params); fail: efi_err("efi_main() failed!\n");
